See Lawson's notes
- Should we transfuse someone Hb 65 g/L? Answer: it depends. When did she start bleeding?
- Bleed acutely - Hb normal. Bleed chronically - Hb low as you pull fluid into the circulation
- Could be more or less dire - depends on her volume status
- If shocked, unwell, continuing to bleed --> transfuse
- Chronic peptic ulcer - gastroenterologist won't see them if Hb low
- Transfuse people to give them oxygen carrying capacity
- Complications of transfusion
- Volume overload
- Blood borne viruses - HIV (<1/10 million), hep B, hep C, malaria, bacterial. Risk unquantifiable. Bacterial most common (because of skin organisms)
- Red cell antibody reactions (ABO reactions - acute hemolysis)
- Delayed reactions
- Febrile, nonhemolytic transfusion reactions (HLA antibodies against contaminating white cells - less common because the blood is filtered)
- We'd give her packed red cells (save the other products for other people; also avoids fluid overload)
- Donating blood: packed red cells, platelets and plasma
- If you get the blood group right, you're probably not going to kill them. If you get it wrong, you probably will.
- Lyse the red cells --> set off complement --> deposit in kidneys --> bad news.
- Rh group: D, C/c or E/e - antibodies can be acquired
- Don't match for Kid or Duffy
- These minor blood groups are not terribly antigenic
- Donated blood has a 6 week expiry date
- If blood gets warm --> hemolysis. If bacteria are in it --> multiply. >30 mins outside the fridge -- throw it out.
- Need to be able to track the unit (275mL) of blood --> inventory management
- Blood products are safer where donation is voluntary and not paid.
Cutoff for transfusion
- Hb <70 g/L: need a good reason NOT TO transfuse
- Hb >100: need a good reason TO transfuse (e.g. thalassemia, they'll not make good rbcs)
- within the highlight region (68-100), individual patient factors determine whether we transfuse
Different Forms of Replacement Therapy
- Packed red cells.
- Fresh frozen plasma.
- Purified protein products (factor concentrates, albumin, Ig).
- M/24 motor vehicle accident
- shocked, hypotensive, major orthopedic and intra-abdominal trauma
- what blood products? crossmatched? what tests?
- resuscitate with whole blood (can't give AB plasma to everyone - because there aren't enough people with this blood type - worth the time to give him the right type of blood). Worth the investment of time in collecting blood
- just give saline/colloid/crystalloid to get BP up
- give O- red cells (can give O+ to men). Give these until you've got blood group, then switch to the right one
- collect blood, blood group (takes a minute)
- give the right type of plasma
- give the right type of red cells
- don't overuse plasma - it can have antibodies we don't always predict (e.g. TRALI - completely unpredictable). Bad if you're well, much worse if you're shocked.
- TRALI is a potentially fatal complication of transfusion
- specific therapy (vitamin K, factor concentrate) not appropriate or available
- correct DIC
- resuscitate people
- scum on bottom of FFP when you thaw it
- rich source of
- factor 8
- factor 13
- die if you cool them too much; so they can contain bacteria - stored at room temperature; short shelf life
- so platelet supply is a problem
- bone marrow failure
- surgery/invasive procedure
- platelet function disorders
- give prophylactic platelets depending on circumstances
- elective open cholecystectomy
- intern ruptures spleen, needs blood NOW
- blood should be group/screened before the surgery
- blood bank will send it in an air tube
- mix together and see if they clag
Selection of the correct unit for transfusion
- ABO and Rh(D) group of the recipient.
- Red cell antibody screen on the recipient:
- Negative Ab screen – electronic crossmatch to be performed.
- Positive Ab screen – antibody identification and serological crossmatch.
- Check for previous records and compare – confirm blood group and previously detected red cell antibodies.
- 72 hour rule: transfusion or pregnancy within three months.
- might be in the process of making an antibody that you haven't detected
- don't give Rh- blood to Rh+ recipient
- group and screen
- if you've not had a transfusion and you're a guy - you probably don't have anyhting other than anti-A and anti-B
- occasionally women who have had kids before, or you've been transfused, you may have non-ABO antibodies
- only 1% of population have anything other than ABO antibodies
- group and screen - check to make sure they're one of the 99% who don't have antibodies to stuff other than ABO
- for thalassemia patients (who are transfused all the time), we need to know all their different antibodies. But for just one off, you just check that you can use group-specific blood.
- A and O most common, people have antibodies to the group that they're not
- Mix the antigen-containing cells from patient with antibodies to various things (A, B, D). They'll clag if there's a positive reaction, to tell you what their type is.
- then you use test cells with their plasma, to check you've done it right
- Cells sink if the reaction doesn't happen. Cells float if reaction does happen
- If you have 3 people who between them contain all of the antigens, you can use it as a quick test whether there are any antibodies (99% of people won't). This lets you screen as to whether you need to do more work.
- Then you can use greater batteries of antigens in particular peoples' blood
- This is much cheaper than doing molecular tests on everyone